How Genetic Disorders Happen

Genetic abnormalities can happen due to small mutation in a single gene,an addition or deletion of an entire chromosome or set of chromosomes.

XX Female, XY MALE

Either of a pair of chromosomes that determine whether an individual is male or female. The sex chromosomes of mammals are designated X and Y; in humans, they constitute one pair of the total 23 pairs of chromosomes. Individuals possessing two X chromosomes (XX) are female; those having one X and one Y chromosome (XY) are male. The X chromosome is larger and carries more genetic information than the Y. Traits controlled only by genes found on the X chromosome (e.g., red-green colour blindness- only males) are said to be sex-linked.

Sex-linked traits occur far more frequently in males than in females, since a male inheriting an allele for a recessive (see recessiveness) trait on the X chromosome lacks a corresponding allele on the Y chromosome that might counteract its effects. Several disorders are associated with an abnormal number of sex chromosomes, including Turner syndrome and Klinefelter syndrome (which we will discuss in class).

Cell Tutorial Game

A somewhat helpful tutorial...
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Fragile X

More common in boys, but girls can also have it.